Pretty much, yeah. Satan + Amon is -50%, which is the most important thing for a team. Well, it's not -50% yet, but should be somewhere this month, I think. Then you have Pluto who is 'lright (and others rate her higher than I do) and Chernobog for an overall damage dealer. It makes a good team (as soon as SSR Amon gets her rebalance).You don't need the Dark Eidolons. 80% with 0 Dark Eidolons is still amazing. Obviously, having 5 Dark sub-Eidolons is better, especially when using double Anubis.
With Anubis, committing to Dark is an option. I guess the best one would be Berith, who would be a sidegrade to Cherno against Light and a decent upgrade everywhere else. I don't know is it worth it, but it is an option.As you said, for Fire it would be either Svarog or Uriel.
For Thunder... Mammon would let you hit -50% without help from Soul, allowing you to run Shingen basically. Awakened Brahma is amazing damage output, but requires her to be at full health after Bursting, so she's unreliable. Athena is the absolute god against Water enemies, so if you only run with elemental advantage, that's certainly a very strong option. Phantom Elemental Lord Awakened Thor is the gambler's choice, allowing you to just outright win any fight whenever the RNG favors you. Marduk will soon get her super powerful Awakening. Tyr will have very good spike damage as soon as her rebalance comes along, not sure when that is.
... holy crap that is a lot of options.
In the end, it comes down to what you want. If you want to build for the next Tower, it'll be Svarog/Uriel. If you want to commit to Dark, Berith. Or if you want to pump your Thunder, well, take your pick. Good luck!
Or just dickpick.